Individuals who decide to have a joint replaced do so because they are in a great deal of pain and/or unable to fully function. However, the underlying cause for their pain and disability can vary. Listed below are some of the diagnoses that most often lead to a joint replacement:

Until recently, osteoarthritis was considered part of aging process and simply a matter of our joints "wearing out." But we now know it's not a normal part of aging, though the incidence of this common, disabling disease does increase with age and become worse over time. Osteoarthritis is a chronic disease of the weight-bearing joints that causes the articular cartilage to deteriorate. When that happens, raw bones rub up against each other, causing pain and disability.

Unlike osteoarthritis, which is a noninflammatory localized disorder, rheumatoid arthritis is a systemic inflammatory disease of the synovial membrane that eventually damages the cartilage. It also eventually leads to raw bones rubbing up against each other, however, resulting in pain and disability.

If the blood supply to a joint is decreased, part of the bone will die and break under weight-bearing activity. The result is a very painful joint that may need to be replaced.